Power consumption is a major problem in today's wireless systems. Although the performance of wireless systems is constantly improving due to increasing demand for higher data rates and additional functionality, power dissipation remains a concern as the housing of wireless communication devices get smaller. Enhancing the battery life of these wireless communication devices is also a challenge because as the performance of wireless systems improves, there is generally a higher burden on battery usage. There also exists a big power-saving requirement for wireless transmission node applications. The wireless communication device in a wireless transmission node can generally be separated into two parts, including a wake-up receiver and a main receiver. In order to reduce power consumption, the main receiver usually operates in a sleep mode and the wake-up receiver operates in a monitoring mode. When the wake-up receiver receives a request signal in the wireless communication environment, it wakes up the main receiver for data transmission. Since the wake-up receiver does not need to perform complex data transmission, the process of long-time monitoring does not consume too much power. The use of the wake-up receiver for monitoring can effectively reduce power consumption, in comparison to the use of the whole wireless receiving device of the wireless communication device for monitoring the request signal.
The wake-up receiver usually needs very high sensitivity, so as to avoid the loss of the request signal in the wireless communication environment. In addition, the wake-up receiver should have a sufficiently large bandwidth for tolerating the reception frequency shift due to variations in environmental temperatures and voltages. However, the sensitivity is negatively correlated with the bandwidth. That is, once the bandwidth is increased, the sensitivity will be reduced. In addition, the operation frequency (reception frequency) of the conventional wake-up receiver cannot be adjusted after the circuit is completely manufactured, and it lacks design flexibility.
In order to solve the problem wherein the sensitivity of the conventional design is limited to the wide bandwidth design and is not adjustable, and in order to further increase the design flexibility of the wake-up receiver, the invention proposes a novel circuit structure for a wireless receiving device and a novel technique for frequency-band calibration of the corresponding wireless receiving device. Such a design can not only maintain the narrow band operation of a circuit, so as to increase the receiving sensitivity, but also includes tunable frequency designs (including tunable bandwidth and frequency), so as to increase the design flexibility of the wake-up receiver, and make the wireless receiving device circuit widely applicable in a variety of wireless communication systems.